docs: document vm.deriveKey

Closes #452

src/SUMMARY.md

@@ -243,6 +243,7 @@
       - [`addr`](./cheatcodes/addr.md)
       - [`sign`](./cheatcodes/sign.md)
       - [`label`](./cheatcodes/label.md)
+      - [`deriveKey`](./cheatcodes/derive-key.md)
     - [Snapshots](./cheatcodes/snapshots.md)
     - [RPC](./cheatcodes/rpc.md)
   - [Forge Standard Library Reference](./reference/forge-std/README.md)

src/cheatcodes/README.md

@@ -70,6 +70,13 @@ interface CheatCodes {
     // Computes address for a given private key
     function addr(uint256 privateKey) external returns (address);
 
+    // Derive a private key from a provided mnenomic string,
+    // or mnenomic file path, at the derivation path m/44'/60'/0'/0/{index}.
+    function deriveKey(string calldata, uint32) external returns (uint256);
+    // Derive a private key from a provided mnenomic string, or mnenomic file path,
+    // at the derivation path {path}{index}
+    function deriveKey(string calldata, string calldata, uint32) external returns (uint256);
+
     // Gets the nonce of an account
     function getNonce(address account) external returns (uint64);
 

src/cheatcodes/derive-key.md

@@ -0,0 +1,41 @@
+## `deriveKey`
+
+### Signature
+
+```solidity
+function deriveKey(
+  string calldata mnemonic,
+  uint32 index
+) external returns (uint256);
+```
+
+```solidity
+function deriveKey(
+  string calldata mnemonic,
+  string calldata path,
+  uint32 index
+) external returns (uint256);
+```
+
+### Description
+
+Derive a private key from a given mnemonic or mnemonic file path.
+
+The first signature derives at the derivation path `m/44'/60'/0'/0/{index}`.
+The second signature allows you to specify the derivation path as the second parameter.
+
+### Examples
+
+Derive the private key from the test mnemonic at path `m/44'/60'/0'/0/0`:
+
+```solidity
+string memory mnemonic = "test test test test test test test test test test test junk";
+uint256 privateKey = vm.deriveKey(mnemonic, 0);
+```
+
+Derive the private key from the test mnemonic at path `m/44'/60'/0'/1/0`:
+
+```solidity
+string memory mnemonic = "test test test test test test test test test test test junk";
+uint256 privateKey = vm.deriveKey(mnemonic, "m/44'/60'/0'/1/", 0);
+```

src/cheatcodes/utilities.md

@@ -3,3 +3,4 @@
 - [`addr`](./addr.md)
 - [`sign`](./sign.md)
 - [`label`](./label.md)
+- [`deriveKey`](./derive-key.md)